Homocinetic fixed joint as a counter track joint

ABSTRACT

The invention relates to a constant velocity fixed ball joint in the form of a counter track joint, comprising an outer joint part with outer tracks, an inner joint part with inner tracks, torque transmitting balls received in pairs of tracks formed of outer tracks and inner tracks, and a ball cage with cage windows in which the balls are held in a common plane and guided on to the angle-bisecting plane when the joint is articulated. First outer tracks, together with first inner tracks, form first pairs of tracks whose control angles open in a first axial direction. Second outer tracks, together with second inner tracks, form second pairs of tracks whose control angles open in a second axial direction, with the control angles being defined as angles between the tangents at the ball contact points in the tracks when the joint is in the aligned condition. The ball cage comprises a spherical outer face with a greatest diameter. The outer joint part forms an introducing aperture for the ball cage with an aperture diameter D 2 &lt;D 1  between the outer tracks. The ball cage, while engaging the outer tracks, can be threaded into the outer joint part in the second axial direction. The outer joint part forms a first stop and guiding face for the spherical outer face of the ball cage. Between the introducing aperture and the first stop and guiding face, the outer joint part comprises a displacement region for the ball cage with an internal diameter of D 3 ≧D 1 . A securing element attached at the outer joint part in front of the introducing aperture forms a second stop and guiding face for the spherical outer face of the ball cage.

DESCRIPTION

[0001] The invention relates to a constant velocity fixed ball joint inthe form of a counter track joint, comprising an outer joint part withouter tracks, an inner joint part with inner tracks, torque transmittingballs which are received in pairs of tracks consisting of outer tracksand inner tracks, and a ball cage with cage windows in which the ballsare held in a common plane and are guided on to the angle-bisectingplane when the joint is articulated; first outer tracks, together withfirst inner tracks, form first pairs of tracks whose control angles openin a first axial direction R₁; second outer tracks, together with secondinner tracks, form second pairs of tracks whose control angles open in asecond axial direction R₂; wherein the control angles are defined asangles between the tangents at the ball contact points in the trackswhen the joint is in the aligned condition. In this embodiment, thecontrol angles are achieved by an axial offset of the centres ofcurvature of the outer tracks and inner tracks in the respectivecomponent relative to a central plane defined by the centres of theballs when the joint is in the aligned condition.

[0002] Constant velocity fixed ball joints in the form of counter trackjoints, as such, are known. With prior art joints of this type it isgenerally proposed that, for the purpose of providing support relativeto the outer joint part and the inner joint part respectively, the outerface of the cage and/or of the inner face of the cage are/is designed soas to be approximately spherical. When mounting such joints, use is madeof the prior art technology of over-articulating when mounting theballs, i.e. first the outer joint part, the ball cage and the innerjoint part are inserted into one another without the balls, whereuponexcessively large articulation angles not achievable in operation areset between the outer joint part and the inner joint part, with theballs being inserted into the cage windows from the outside in differentarticulation positions.

[0003] It is the object of the present invention to provide a joint ofsaid type which, while having advantageous strength and ball guidingconditions, permits a simplified assembly method.

[0004] The objective is achieved in that the ball cage has a sphericalouter face with a greatest diameter D₁; that the outer joint part formsan introducing aperture for the ball cage with an aperture diameterD₂<D₁ measured between the outer tracks; that the ball cage, in engagingthe outer tracks, can be threaded into the outer joint part in thesecond axial direction R₂; that the outer joint part forms a first stopand guiding face for the spherical outer face of the ball cage, whichfirst stop and guiding face supports the ball cage in the outer jointpart; that between the introducing aperture and the first stop andguiding face, the outer joint part comprises a displacement region forthe ball cage with an internal diameter of D₃≧D₁; and that a securingelement attached at the outer joint part in front of the introducingaperture forms a second stop and guiding face for the spherical outerface of the ball cage, which second stop and guiding face axially fixesthe ball cage relative to the first stop and guiding face.

[0005] The above-described characteristics necessitate a conventionalassembly of the ball cage and outer joint part by threading the websbetween the cage windows of the ball cage into the outer tracks of theouter joint part, but subsequently permit the inner joint part to beaxially mounted in the pre-assembled unit consisting of the outer jointpart and ball cage with inserted balls wherein the outer joint part andsaid pre-assembled unit can be slid into one another in a coaxialposition and wherein in one assembly position, the ball cage in theouter joint part is pulled in the direction of the introducing aperture,with the first balls in the first ball tracks being displaced outwardlyby the maximum amount, whereupon the inner joint part is slid throughthe displaced balls into the outer joint part. Thereafter, the ball cageis moved away from the introducing aperture over the displacement regionin the outer joint part. After the ball cage has abutted the first stopand guiding face in the outer joint part, the joint is secured by asecuring element attached to the outer joint part. By making use of arecess at the open end of the outer joint part, which recess, ascompared to the greatest outer diameter of the ball cage, produces asmaller introducing aperture, the wrapping region of the outer tracksfor the balls at the introducing aperture and therebehind as far as thedisplacement region in the outer joint part can be increased. Insofar asreference is made here to the introducing aperture of the outer jointpart with reference to the assembly operation of joints with aseparately produced base and also in the case of disc joints, this canalso be the aperture pointing to the base, and the securing element tobe attached can be the joint base itself or an annular or cover elementinserted between the outer joint part and the joint base.

[0006] In the case of this assembly operation, the balls, especially incases where the ball cage is coaxially aligned relative to the outerjoint part, the balls are inserted from the inside of the ball cage intothe cage windows and into the outer tracks. It is also possible toproceed in such a way that the balls—with the ball cage beingarticulated relative to the outer joint part—are inserted individuallyfrom the outside into the cage windows and pivoted into the outertracks.

[0007] In view of the above-mentioned assembly method it is possible,according to a preferred embodiment, that the inner joint part isproduced so as to be integral with a joint journal or shaft shank, whichincreases the strength and reduces the number of parts.

[0008] According to a particularly advantageous embodiment it isproposed that the ball cage comprises an introducing aperture for theinner joint part through which the inner joint part can be introduced inthe second axial direction R₂ in a coaxial position relative to the ballcage. In particular, it is possible for the inner face of the ball cageto be undercut-free when viewed in said second axial direction.

[0009] According to a preferred embodiment it is proposed that the ballcage, on its inside, forms a stop and guiding face for a spherical outerface of the inner joint part. However, such a contact between the innerjoint part and the ball cage is not compulsory. Axial fixing of theinner joint part relative to the ball cage can also be effected in bothaxial directions indirectly via ball tracks, balls and cage windows.

[0010] As already mentioned in connection with the possible assemblymethod, the securing element can be an annular additional elementattached at the joint aperture of the outer joint part or individualwedge elements formed on or attached thereto, with the second axialdirection pointing from the joint aperture to the joint centre, whereasas an alternative thereto, the securing element can be the joint baseproduced separately from the outer joint part, or it could be an annularor cover-shaped additional element inserted between the outer joint partand the joint base, wherein said second axial direction points from thejoint base to the joint centre.

[0011] Particular advantages of the inventive joint consist in that thecage, because of its contour which is undercut-free on the inside, iseasy to produce from a production-technical point of view, for exampleby being formed by a punch.

[0012] Preferred embodiments of the invention as well as the assemblymethod will be explained below with reference to the drawings wherein

[0013]FIG. 1 shows an inventive fixed counter track joint in a firstembodiment with an outer joint part produced in one piece

[0014] a) in a longitudinal section through a ball track plane

[0015] b) in a longitudinal section through a plane between ball tracks

[0016] in a finish-assembled condition.

[0017]FIG. 2 shows an inventive fixed counter track joint with an outerjoint part produced in one piece according to FIG. 1

[0018] a) in a longitudinal section through a ball track plane

[0019] b) in a longitudinal section through a plane between ball tracks

[0020] during the axial mounting of the inner joint part.

[0021]FIG. 3 shows an inventive fixed counter track joint with an outerjoint part produced in one piece according to FIG. 11

[0022] a) in a longitudinal section through a plane between ball tracksas in FIG. 2b

[0023] b) the enlarged detail X according to FIG. 3a.

[0024]FIG. 4 shows an inventive fixed counter track joint in a secondembodiment with a welded-on joint base

[0025] a) in a longitudinal section through a ball track plane

[0026] b) in a longitudinal section through a plane between ball tracks

[0027] in a finish-assembled condition.

[0028]FIG. 5 shows the inventive fixed counter track joint with awelded-on joint base according to FIG. 4

[0029] a) in a longitudinal section through a plane between ball tracksas in FIG. 4b,

[0030] b) the enlarged detail X according to FIG. 5a.

[0031] Below, the various sections and illustrations of the individualFigures will be described jointly.

[0032] Below, FIGS. 1 to 3 will be described jointly.

[0033] FIGS. 1 to 3 each show an inventive constant velocity fixed joint11 comprising an outer joint part 12 with a formed-on journal 13, aninner joint part 14 with a formed-on journal 15, balls 16 ₁, 16 ₂, aball cage 17 and a securing element 18. The joint is provided in theform of a counter track joint, i.e. first outer ball tracks 19 ₁ in theouter joint part 12 and first inner ball tracks 20 ₁ in the inner jointpart 14 which hold first balls 16 ₁ axially develop oppositely to thatof second outer ball tracks 19 ₂ in the outer joint part 12 and secondinner ball tracks 20 ₂ in the inner joint part 14 which hold secondballs 16 ₂. The first pairs of tracks 19 ₁, 20 ₁ have control angleswhich open in the first direction R₁ and the second pairs of tracks 19₂, 20 ₂ have control angles which open in the second direction R₂. Thetracks are provided in the form of Rzeppa tracks, i.e. their trackcentre lines (not shown), like the identifiable track base lines, extendin the form of circular arches whose centres, with reference to theassociated tracks 19 ₁, 20 ₁, 19 ₂, 20 ₂ are axially offset relative toone another. The counter track formation is obtained in that the centresof curvature of the outer tracks 19 ₁, 19 ₂ in the outer joint part arecircumferentially alternately offset in opposite axial directionsrelative to the central joint plane and the centres of curvature of theinner ball tracks 20 ₁, 20 ₂ in the inner joint part 14 arecircumferentially alternately offset in the opposite axial directionrelative to the central joint plane. The central joint plane is definedby the centres of the balls. In the outer joint part 14 there isaccommodated the ball cage 17 with a spherical outer face 23 whosegreatest outer diameter has been given the reference symbol D₁. In themounted position according to FIG. 1, the ball cage 17 is directly fixedin the second direction R₂ by the outer joint part which forms a firststop and guiding face 21 and in the first direction R₁ by an attachedsecuring element 18 which forms a second stop and guiding face 22. As isparticularly obvious in FIG. 2, the ball cage 17 is axially displaceableinside the outer joint part in an internally cylindrical displacementregion 24 in the coaxial position relative to the outer joint part,which displacement region 24, towards the introducing aperture 25, isdelimited by a recess 26 and towards the joint base 12 and the journal13 respectively by the first stop and guiding face 21. As a result ofthe recess 26, the aperture diameter D₂ of the introducing aperture 25is smaller than the above-mentioned greatest outer diameter D₁ of theball cage. In the displacement region 24, the inner diameter D₃ of theouter joint part is greater than/equal to the greatest outer diameter D₁of the ball cage. This configuration means that the ball cage, in a wayknown in itself, has to be threaded in direction R₁ into the outer jointpart 14, i.e. the ball cage is rotated around a transverse axis by 90°and then rolled into the outer joint part while the webs between theouter tracks are introduced into the cage windows. Thereafter the cageis rotated back around said transverse axis by 90°, to get into thecoaxial position relative to the outer joint part. Hereafter, the ballcage, as shown with reference to the inventive joint in FIGS. 2 and 3,is pulled within the displacement region 24 towards the introducingaperture 25. It is in this position that the balls are introduced; thefirst balls 16 ₁ can be displaced outwardly in the outer tracks 19 ₁ tosuch an extent that the inner joint part 14 can be introduced coaxiallythrough an introducing aperture 29 in the ball cage 17 into same, withthe first balls 16 ₁ being able to enter, without being obstructed, thefirst tracks 20 ₁. Thereafter, the ball cage 17, with its sphericalouter face 23, is moved as far as the first stop and guiding face 21 andthe inner joint part 14, with its spherical outer face 27, is moved asfar as the undercut-free stop and guiding face 28 in the ball cage 17.In this position, the parts are then secured by the securing element 18whose second stop and guiding face 22 now holds the ball cage 17 againstthe first stop and buiding face 21.

[0034] Now, FIGS. 4 and 5 will be described jointly below.

[0035]FIGS. 4 and 5 each show an inventive constant velocity fixed joint41 comprising an outer joint part 42 with an attached base 48 and anadjoining journal 43, an inner joint part 44 with a formed-on journal45, balls 46 ₁, 46 ₂, and a ball cage 47. The directions R₁, R₂essential for assembly purposes have been exchanged relative to thejoint of the previous embodiment. The base 48 forms the securingelement. The joint is provided in the form of a counter track joint,i.e. first outer ball tracks 49 ₁ in the outer joint part 42 and firstinner ball tracks 50 ₁ in the inner joint part 44 which hold the balls46 ₁ axially develop oppositely to that of second outer ball tracks 49 ₂in the outer joint part 42 and second inner ball tracks 50 ₂ in theinner joint part 44 which hold second balls 46 ₂. The tracks areprovided in the form of Rzeppa tracks, i.e. their track centre lines(not shown), like the identifiable track base lines, extend in the formof circular arches whose centres, with reference to the associatedtracks 49 ₁, 20 ₁,49 ₂, 20 ₂ are axially offset relative to one another.The counter track formation is obtained in that the centres of curvatureof the outer tracks 49 ₁, 49 ₂ in the outer joint part arecircumferentially alternately offset in opposite axial directionsrelative to the central joint plane and the centres of curvature of theinner ball tracks 50 ₁, 50 ₂ in the inner joint part arecircumferentially alternately offset in the opposite axial directionrelative to the central joint plane. The central joint plane is definedby the centres of the balls. In the outer joint part 44 there isaccommodated the ball cage 47 with a spherical outer face 53 whosegreatest outer diameter has been given the reference symbol D₁. In themounted position according to FIGS. 4, 5, the ball cage 47 is directlyfixed in the second direction R₂ by the outer joint part which forms afirst stop and guiding face 51 and in the first direction R₁ by theattached base 48 which forms a second stop and guiding face 52. Asshown, the base 48 can either be welded on or threaded on. As isparticularly obvious from the details in FIG. 5, the ball cage 47 isaxially displaceable inside the outer joint part in an internallycylindrical displacement region 24 in a coaxial position relative to theouter joint part, which displacement region 54, in the first directionR₁, towards the introducing aperture 55 closed by the base 48, isdelimited by a recess 56 and in the second direction R₂, towards thejournal 45 by the first stop and guiding face 51. As a result of therecess 56, the aperture diameter D₂ of the introducing aperture 55 issmaller than the above-mentioned greatest outer diameter D₁ of the ballcage. In the displacement region 24, the inner diameter D₃ of the outerjoint part is greater than/equal to the greatest outer diameter D₁ ofthe ball cage. This configuration means that the ball cage, with thebase 48 having been removed, has to be threaded in direction R₁ into theouter joint part 44, i.e. the ball cage is rotated around a transverseaxis by 90° and then rolled into the outer joint part, while the websare introduced between the outer tracks into the cage windows.Hereafter, the ball cage is rotated back by 90° around said transverseaxis in order to reach the coaxial position relative to the outer jointpart. Thereafter, the ball cage of the inventive joint according to FIG.2 is pulled within the displacement region 54 towards the introducingaperture 55. It is in this position that the balls are introduced; thefirst balls 46 ₁ can be displaced outwardly in the outer tracks 49 ₁ tosuch an extent that the inner joint part 44 can be introduced coaxiallythrough an introducing aperture 59 in the ball cage 47 into same, withthe first balls 46 ₁ being able, without being obstructed, to enter thefirst tracks 50 ₁. Thereafter, the ball cage 47, with its sphericalouter face 53, is moved as far as the first stop and guiding face 51 andthe inner joint part 44, with its spherical outer face 57, is moved asfar as the undercut-free stop and guiding face 58 in the ball cage 47.In this position, the parts are then secured by mounting the base 48whose second stop and guiding face 52 now holds the ball cage 47 againstthe first stop and guiding face 51.

[0036] List of Reference Numbers

[0037]11, 41 joint

[0038]12, 42 outer joint part

[0039]13, 43 journal

[0040]14, 44 inner joint part

[0041]15, 45 journal

[0042]16, 46 ball

[0043]17, 47 ball cage

[0044]18 securing element

[0045]48 base

[0046]19, 49 outer track

[0047]20, 50 inner track

[0048]21, 51 guiding face 1

[0049]22, 52 guiding face 2

[0050]23, 53 outer face of cage

[0051]24, 54 displacement region

[0052]25, 55 introducing aperture

[0053]26, 56 recess

[0054]27, 57 outer face of inner joint part

[0055]28, 58 stop and guiding face

[0056]29, 59 introducing aperture (17, 47)

1. A constant velocity fixed ball joint (11, 41) in the form of a counter track joint, comprising an outer joint part (12, 42) with outer tracks (19, 49), an inner joint part (14, 44) with inner tracks (20, 50), torque transmitting balls (16, 46) which are received in pairs of tracks consisting of outer tracks and inner tracks, and a ball cage (17, 47) with cage windows (26, 56) in which the balls (16, 46) are held in a common plane and are guided on to the angle-bisecting plane when the joint is articulated; first outer tracks (19 ₁, 49 ₁), together with first inner tracks (20 ₁, 50 ₁), form first pairs of tracks whose control angles open in a first axial direction R₁; second outer tracks (19 ₂, 49 ₂), together with second inner tracks (20 ₂, 50 ₂), form second pairs of tracks whose control angles open in a second axial direction R₂; wherein the control angles are defined as angles between the tangents at the ball contact points in the tracks when the joint is in the aligned condition; the ball cage (17, 47) has a spherical outer face (23, 53) with a greatest diameter D₁; the outer joint part (12, 42) forms an introducing aperture (25, 53) for the ball cage (17, 47) with an aperture diameter D₂<D₁ measured between the outer tracks (19, 49); the ball cage (17, 47), in engaging the outer tracks (19, 49), can be threaded into the outer joint part (12, 42) in the second axial direction R₂; the outer joint part (12, 42) forms a first stop and guiding face (21, 51) for a spherical outer face (23, 53) of the ball cage; between the introducing aperture (25, 55) and the first stop and guiding face (21, 51), the outer joint part (21, 42) comprises a displacement region (24, 54) for the ball cage with an internal diameter of D₃≧D₁; a securing element (18, 48) attached at the outer joint part in front of the introducing aperture (25, 55) forms a second stop and guiding face (22, 52) for the spherical outer face (23, 53) of the ball cage.
 2. A joint according to claim 1, characterised in that the ball cage (17, 47) comprises an introducing aperture (29, 59) for the inner joint part (14, 44) through which the inner joint part (14, 44) can be introduced in the second axial direction R₂ in a coaxial position relative to the ball cage.
 3. A joint according to claim 2, characterised in that the inner face of the ball cage (17, 47) is undercut-free if viewed in said second axial direction R₂.
 4. A joint according to any one of claims 1 to 3, characterised in that the ball cage (17, 47), on its inside, forms a stop and guiding face (28, 58) for a spherical outer face (27, 57) of the inner joint part (14, 44).
 5. A joint according to any one of claims 1 to 4, characterised in that the inner joint part (14, 44) is produced so as to be integral with a joint journal (15, 45).
 6. A joint according to any one of claims 1 to 5, characterised in that the securing element is provided in the form of an annular element (18) attached at the joint aperture (30) of the outer joint part (12) and that said second axial direction R₂ points from the joint aperture (30) to the central joint plane. (FIGS. 1 to 3).
 7. A joint according to any one of claims 1 to 5, characterised in that the securing element comprises individual wedge elements attached to or formed on at the joint aperture of the outer joint part and that said second axial direction R₂ points from the joint aperture to the central joint plane. (without Figure)
 8. A joint according to any one of claims 1 to 5, characterised in that the securing element is the joint base (48) formed separately from the outer joint part (42) and that said second axial direction R₂ points from the joint base (48) to the central joint plane. (FIGS. 4, 5)
 9. A joint according to any one of claims 1 to 5, characterised in that the securing element is formed by an additional annular or cover element inserted between the outer joint part and the joint base and that said second axial direction R₂ points from the joint base to the central joint plane. (without Figure)
 10. A method of assembling a constant velocity fixed ball joint according to any one of claims 1 to 9, characterised by the following stages: the ball cage (17, 47), in engaging the outer tracks (19, 49) of the outer joint part (12, 42), is introduced into the outer joint part through the introducing aperture (25, 55) for the ball cage (17, 47); the cage windows (26, 56) are made to correspond to the outer tracks (19, 49) and the balls (16, 46) are inserted into the cage windows (26, 56) and into the outer tracks (19, 49); with the outer joint part (12, 42) and the ball cage (17, 47) being coaxially aligned, the configuration consisting of ball cage (17, 47) and balls (16, 46) is displaced within the displacement region (24, 54) towards the introducing aperture (25, 55) for the ball cage; the inner joint part (14, 44), while being co-axially aligned relative to the outer joint part (12, 42) and to the ball cage (17, 47), is introduced through the introducing ing aperture (29, 59) for the inner joint part (14, 44) into the ball cage (17, 47); the configuration consisting of ball cage (17, 47), balls (16, 46) and inner joint part (14, 44) is axially displaced until the ball cage (17, 47) stops against the first stop and guiding face (21, 51), and while the second stop and guiding face (22, 52) stops against the ball cage (17, 47), the securing element (18, 48) is attached at the outer joint part (12, 42).
 11. A method according to claim 10, characterised in that the balls—especially with the ball cage (17, 47) being coaxially aligned relative to the outer joint part (12, 42)—are inserted from the inside of the ball cage into the cage windows (26, 56) and into the outer tracks (19,
 12. A method according to claim 10, characterised in that, with the ball cage (17, 47) being articulated relative to the outer joint part (12, 42), the balls are inserted individually from the outside into the cage windows (26, 56) and pivoted into the outer tracks (19, 49). 